Real-time ground motion from the new strong motion seismic network in British Columbia, Canada

Abstract

Canada's chief vulnerability to earthquakes is concentrated in a few urban regions. The south-west coast of the province of British Columbia is subject to the hazard posed by the Cascadia subduction zone with the associated earthquake scenarios of shallow crustal events, deeper subcrustal events and magnitude 9 megathrust earthquakes. The Geological Survey of Canada operates a new real-time ground motion reporting network of accelerographs in British Columbia. As of January 2006, one hundred instruments have been deployed, most concentrated in and around the urban centres of Vancouver and Victoria. The instruments combine several functions, serving as continuously recording strong motion accelerographs, and, at the same time, as sensors which automatically detect events and report real-time ground motion parameters such as peak ground acceleration (PGA), velocity (PGV), and spectral intensity (SI). Instruments form a network using various physical means of communications, including wired, wireless and satellite Internet links. Standard Internet protocols are employed to convey ground motion reports. The network thus does not depend on the existence of a seismic data centre to analyze full waveform data, generate an alarm and subsequently disseminate ground motion maps. Instead, ground motion parameters from an instrument are relayed directly to disaster response agencies and lifeline and critical infrastructure operators. A prototype client system, which depicts peak ground motion values on a thematic map, is in operation with the Ministry of Transportation in British Columbia. The reliability of alarms from this network as well as the quality of the generated shake maps depend primarily on station density. Since the instruments are inexpensive to own, deploy, and operate, dense arrays have become a realistic proposition.